Formic acid is typically produced commercially by a two-step process. Methanol is first carbonylated to yield methyl formate. Then, the methyl formate is hydrolyzed to generate formic acid and methanol. Although the carbonylation of methanol is a straightforward process, the hydrolysis of methyl formate to form formic acid has a very poor equilibrium constant (Keq≈0.2 at 25° C.). As a result, the maximum yield of formic acid from this process is very low.
A possible solution to this problem would be to use other alkyl formate species that have better hydrolysis equilibria. While direct carbonylation of secondary and tertiary alcohols is a viable route to produce these other formate species, the carbonylation reactions, especially ones involving tertiary alcohols, are generally low-yielding and often require higher temperatures and much higher carbon monoxide pressures.
Accordingly, there is a need for more efficient and greener processes for synthesizing secondary and tertiary formate esters from methanol, particularly without using the toxic CO gas.
The present invention addresses this need as well as others, which will become apparent from the following description and the appended claims.